Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Hydrilla verticillata
(hydrilla)

Toolbox

Datasheet

Hydrilla verticillata (hydrilla)

Summary

  • Last modified
  • 24 July 2018
  • Datasheet Type(s)
  • Invasive Species
  • Pest
  • Host Plant
  • Preferred Scientific Name
  • Hydrilla verticillata
  • Preferred Common Name
  • hydrilla
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Monocotyledonae
  • Summary of Invasiveness
  • H. verticillata is a submerged fast-growing aquatic herb. It has a highly effective survival strategy that makes it one of the most troublesome aquatic weeds of water bodies in the world. It ...

Don't need the entire report?

Generate a print friendly version containing only the sections you need.

Generate report

Pictures

Top of page
PictureTitleCaptionCopyright
Hydrilla verticillata (hydrilla); habit.
TitleHabit
CaptionHydrilla verticillata (hydrilla); habit.
Copyright©Leslie J. Mehrhoff/University of Connecticut/Bugwood.org - CC BY 3.0 US
Hydrilla verticillata (hydrilla); habit.
HabitHydrilla verticillata (hydrilla); habit.©Leslie J. Mehrhoff/University of Connecticut/Bugwood.org - CC BY 3.0 US
Hydrilla verticillata (hydrilla); plant in hand, showing general appearance.
TitleHabit
CaptionHydrilla verticillata (hydrilla); plant in hand, showing general appearance.
Copyright©Leslie J. Mehrhoff/University of Connecticut/Bugwood.org - CC BY 3.0 US
Hydrilla verticillata (hydrilla); plant in hand, showing general appearance.
HabitHydrilla verticillata (hydrilla); plant in hand, showing general appearance.©Leslie J. Mehrhoff/University of Connecticut/Bugwood.org - CC BY 3.0 US
Hydrilla verticillata (hydrilla); plant in hand, showing general appearance.
TitleHabit
CaptionHydrilla verticillata (hydrilla); plant in hand, showing general appearance.
Copyright©Leslie J. Mehrhoff/University of Connecticut/Bugwood.org - CC BY 3.0 US
Hydrilla verticillata (hydrilla); plant in hand, showing general appearance.
HabitHydrilla verticillata (hydrilla); plant in hand, showing general appearance.©Leslie J. Mehrhoff/University of Connecticut/Bugwood.org - CC BY 3.0 US
Hydrilla verticillata (hydrilla); morphology and scale.
TitleMorphology
CaptionHydrilla verticillata (hydrilla); morphology and scale.
Copyright©Leslie J. Mehrhoff/University of Connecticut/Bugwood.org - CC BY 3.0 US
Hydrilla verticillata (hydrilla); morphology and scale.
MorphologyHydrilla verticillata (hydrilla); morphology and scale.©Leslie J. Mehrhoff/University of Connecticut/Bugwood.org - CC BY 3.0 US
Hydrilla verticillata (hydrilla); root bulbs in hand.
TitleRoot bulbs
CaptionHydrilla verticillata (hydrilla); root bulbs in hand.
Copyright©Robert Vidéki/Doronicum Kft./Bugwood.org - CC BY-NC 3.0 US
Hydrilla verticillata (hydrilla); root bulbs in hand.
Root bulbsHydrilla verticillata (hydrilla); root bulbs in hand.©Robert Vidéki/Doronicum Kft./Bugwood.org - CC BY-NC 3.0 US
Hydrilla verticillata (hydrilla); invasive habit. USA. August 2011.
TitleInvasive habit
CaptionHydrilla verticillata (hydrilla); invasive habit. USA. August 2011.
Copyright©Cleveland Metroparks/Bugwood.org - CC BY-NC 3.0 US
Hydrilla verticillata (hydrilla); invasive habit. USA. August 2011.
Invasive habitHydrilla verticillata (hydrilla); invasive habit. USA. August 2011.©Cleveland Metroparks/Bugwood.org - CC BY-NC 3.0 US
Hydrilla verticillata (hydrilla); tangled on a boats outboard motor. USA.
TitleHazard
CaptionHydrilla verticillata (hydrilla); tangled on a boats outboard motor. USA.
Copyright©Wilfredo Robles/Mississippi State University/Bugwood.org - CC BY 3.0 US
Hydrilla verticillata (hydrilla); tangled on a boats outboard motor. USA.
HazardHydrilla verticillata (hydrilla); tangled on a boats outboard motor. USA.©Wilfredo Robles/Mississippi State University/Bugwood.org - CC BY 3.0 US
Hydrilla verticillata (hydrilla); invasive habit on a American lake; Mike Netherland (left) and Donald Morgan of the Army Corps of Engineers collect herbicide-resistant hydrilla from Lake Seminole in northern Florida. July 2005.
TitleInvasive habit
CaptionHydrilla verticillata (hydrilla); invasive habit on a American lake; Mike Netherland (left) and Donald Morgan of the Army Corps of Engineers collect herbicide-resistant hydrilla from Lake Seminole in northern Florida. July 2005.
CopyrightPublic Domain - Released by the USDA-ARS/original image by Stephen Ausmus
Hydrilla verticillata (hydrilla); invasive habit on a American lake; Mike Netherland (left) and Donald Morgan of the Army Corps of Engineers collect herbicide-resistant hydrilla from Lake Seminole in northern Florida. July 2005.
Invasive habitHydrilla verticillata (hydrilla); invasive habit on a American lake; Mike Netherland (left) and Donald Morgan of the Army Corps of Engineers collect herbicide-resistant hydrilla from Lake Seminole in northern Florida. July 2005.Public Domain - Released by the USDA-ARS/original image by Stephen Ausmus
Hydrilla verticillata (hydrilla); leaf, under high magnification. Original x400.
TitleLeaf
CaptionHydrilla verticillata (hydrilla); leaf, under high magnification. Original x400.
Copyright©John Alan Elson/via wikipedia/ http://www.3dham.com/vegetable/index.html - CC BY-SA 3.0
Hydrilla verticillata (hydrilla); leaf, under high magnification. Original x400.
LeafHydrilla verticillata (hydrilla); leaf, under high magnification. Original x400.©John Alan Elson/via wikipedia/ http://www.3dham.com/vegetable/index.html - CC BY-SA 3.0
Hydrilla verticillata (hydrilla); a, Leaf; b, spathe filled with male flowers; c, empty spathe; d, free-floating male flower; e, female flower; f, fruit; g, seed.
TitleMorphology
CaptionHydrilla verticillata (hydrilla); a, Leaf; b, spathe filled with male flowers; c, empty spathe; d, free-floating male flower; e, female flower; f, fruit; g, seed.
Copyright©SEAMEO-BIOTROP
Hydrilla verticillata (hydrilla); a, Leaf; b, spathe filled with male flowers; c, empty spathe; d, free-floating male flower; e, female flower; f, fruit; g, seed.
MorphologyHydrilla verticillata (hydrilla); a, Leaf; b, spathe filled with male flowers; c, empty spathe; d, free-floating male flower; e, female flower; f, fruit; g, seed.©SEAMEO-BIOTROP

Identity

Top of page

Preferred Scientific Name

  • Hydrilla verticillata (L. f.) Royle

Preferred Common Name

  • hydrilla

Other Scientific Names

  • Elodea verticillata F.Muell.
  • Hydora lithuanica (Rchb.) Besser
  • Hydrilla alternifolia
  • Hydrilla angustifolia Hassk.
  • Hydrilla dentata Casp.
  • Hydrilla dregeana Presl
  • Hydrilla japonica
  • Hydrilla lithuanica (Besser) Dandy
  • Hydrilla muscoides Planch.
  • Hydrilla najadifolia Zoller & Mortizi
  • Hydrilla polysperma Blatt.
  • Hydrilla roxburghii Steud.
  • Hydrilla subulata Royle
  • Hydrilla wightii Planch.
  • Hydrospondylus submersus Hassk.
  • Serpicula verticillata L.f.
  • Udora lithuanica Rchb.
  • Udora occidentalis W.D.J.Koch
  • Udora pomeranica Rchb.
  • Udora verticillata Spreng.
  • Vallisneria verticillata Roxb.

International Common Names

  • English: esthwaite waterweed; water thyme; waterthyme
  • Spanish: maleza acuática
  • French: Hydrilla de Lithuanie
  • Chinese: hei zao

Local Common Names

  • Cuba: hidrila
  • Germany: Guinduetzel; Quirllboettrige; Wasserquirl
  • Japan: kinomo
  • USA: hydrilla; water weed

EPPO code

  • HYLLI (Hydrilla lithuanica)
  • HYLVE (Hydrilla verticillata)

Summary of Invasiveness

Top of page

H. verticillata is a submerged fast-growing aquatic herb. It has a highly effective survival strategy that makes it one of the most troublesome aquatic weeds of water bodies in the world. It has the potential to alter fishery populations, cause shifts in zooplankton communities and affect water chemistry. It forms dense masses, outcompeting native plants and interfering with many uses of waterways. It is readily dispersed by movement of plant fragments and can produce up to 6,000 tubers per m2. Tubers can remain viable for several days out of water or for over 4 years in undisturbed sediment. They are not impacted by most management activities, and a small percentage can sprout throughout the year making the species very difficult to manage or eradicate. It can be spread by water flow, waterfowl and recreational activities and is sold as an aquarium plant. Currently, this species is considered as one of the most aggressive invasive species in aquatic habitats. In the USA it has been listed as a Federal Noxious Weed since 1976, and is regarded as one of the worst invasive aquatic weed problems in Florida and much of the country. Its import is prohibited in Western Australia and Tasmania, and it is on the EPPO alert list.

Taxonomic Tree

Top of page
  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Monocotyledonae
  •                     Order: Hydrocharitales
  •                         Family: Hydrocharitaceae
  •                             Genus: Hydrilla
  •                                 Species: Hydrilla verticillata

Notes on Taxonomy and Nomenclature

Top of page

The family Hydrocharitaceae comprises 18 genera and 116 species of aquatic herbs. Members of this family are both fresh-water and marine aquatic species (Stevens, 2012). Hydrilla is a monotypic genus. H. verticillata exhibits a degree of phenotypic plasticity in response to age, habitat conditions, and water quality. The family is notable for the unique pollination mechanism of some genera (e.g., Elodea, Enhalus, Hydrilla, and Vallisneria). The male flowers become detached and float about until they encounter and transfer pollen to a female flower, which has reached the surface of the water by means of an elongated stalk. After pollination, the developing fruit is drawn under the water to finish ripening.

Description

Top of page

H. verticillata is a submerged, monoecious or dioecious perennial. Its stems are branched, about 1 mm thick and up to 3 m long; the internodes are 3 to 50 mm long. The sessile leaves are formed in whorls at the nodes; there are 3-8, sometimes up to 12 leaves in a whorl. The leaves are 7-40 mm long, linear to lanceolate, with a conspicuous midrib. They have sharply toothed margins and spines on the vein on the lower side of the leaves; a few teeth may also be formed on this vein. These leaf characteristics are commonly used to distinguish H. verticillata from similar submerged plants in the Hydrocharitaceae, like Egeria and Elodea spp.

The inflorescences are unisexual, arising from spathes situated in the leaf axils, each flower has three sepals and three petals. All six perianth parts are clear or translucent green (the sepals usually slightly reddish).The male spathe is about 1.5 mm long, solitary in the leaf axils, somewhat spiny. The female spathe is about 5 mm long, solitary in the leaf axils. There are three petals, three stamens and three styles. The ovary is cylindrical to narrowly conical and is enclosed in the base of a hypanthium; the style is as long as the hypanthium and there are three stigmas. For further information, see Cook et al. (1974) and Aston (1977).

The fruit is cylindrical, about 7 mm long and 1.5 mm wide. It contains 2-7 oblong-elliptic seeds. For further information, see Cook and Lüönd (1982); Swarbrick et al. (1981); and Yeo et al. (1984).

Plant Type

Top of page Annual
Aquatic
Herbaceous
Perennial
Seed propagated
Vegetatively propagated

Distribution

Top of page

H. verticillata has a wide and rather disjointed geographical range (see Pieterse, 1981; Cook and Lüönd, 1982, Preston and Croft, 1997). This range includes South-East Asia, Australia, Central Africa, a few sites in Europe and, since at least the early 1960s, the USA and the Panama Canal area. In Asia, it is found from Iran and Afghanistan through Pakistan and India to South-East Asia, reaching northwards to Japan, Korea and Manchuria, China. It was first recorded on north Iraqi rivers by Al-Mandeel (2013). It is thought to be native to Africa and south and southeast Asia (Zhuang and Beentje, 2017)).The common dioecious type of H. verticillata is thought to originate from the Indian subcontinent, whereas the origin of the monoecious type is likely to be Korea (Madeira et al., 1997). It also occurs in the Moluccas, Indonesia and Papua New Guinea. In the Indian Ocean it occurs on Mauritius, Réunion and Madagascar. In the Pacific Ocean it has been found on Fiji and Guam. It is a common plant in the northern and western parts of Australasia and it also occurs in the North Island of New Zealand.

On the African continent it occurs around Lake Victoria and Lake Tanganyika in the Rift Valley of East Africa, while it has also been reported from Mozambique and a few isolated places in West Africa and, in 2006, from South Africa. It is thought to be native but is relatively rare in Europe (Preston and Croft, 1997), sufficiently so that it is protected in Lithuania (Balevicius, 1998). It occurs in certain areas in Poland and Belarus, and has been found in solitary lakes in Ireland (Preston and Croft, 1997).

At least three different strains of H. verticillata have spread to the USA and the Panama Canal area. The first record is of the dioecious strain in the early 1950s which was imported for use in aquariums; other strains were separate introductions (Jacono, 2011). At present it occurs throughout the Gulf States, in southern California, and in certain localities in the eastern and central parts of the country. For a detailed description of the distribution in the USA, see Jacono et al. (2011). There are recent reports from South America (Brazil) and Caribbean islands. It was locally introduced into the La Gamba valley of southern Costa Rica in 2005 (Haider et al., 2016).

Distribution Table

Top of page

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

AfghanistanPresentNativeCook and Lüönd, 1982; Govaerts, 2016
BangladeshRestricted distributionPieterse, 1981; Cook, 1996; EPPO, 2014; Govaerts, 2016
BhutanPresentNativeGovaerts, 2016
Brunei DarussalamPresentWaterhouse, 1993
CambodiaRestricted distributionPieterse, 1981; EPPO, 2014; Govaerts, 2016
ChinaRestricted distributionPieterse, 1981; EPPO, 2014
-AnhuiPresentNativeFlora of China Editorial Committee, 2016
-FujianPresentNativeFlora of China Editorial Committee, 2016
-GuangdongPresentNativeFlora of China Editorial Committee, 2016
-GuangxiPresentNativeFlora of China Editorial Committee, 2016
-GuizhouPresentNativeFlora of China Editorial Committee, 2016
-HainanPresentNativeFlora of China Editorial Committee, 2016
-HebeiPresentNativeFlora of China Editorial Committee, 2016
-HeilongjiangPresentNativeFlora of China Editorial Committee, 2016
-HenanPresentNativeFlora of China Editorial Committee, 2016
-HubeiPresentZhou and Chen, 1996; Flora of China Editorial Committee, 2016
-HunanPresentNativeFlora of China Editorial Committee, 2016
-JiangsuPresentZhu et al., 1993; Zhang et al., 1999; Flora of China Editorial Committee, 2016
-JiangxiPresentNativeFlora of China Editorial Committee, 2016
-LiaoningPresentNativeFlora of China Editorial Committee, 2016
-ShandongPresentNativeFlora of China Editorial Committee, 2016
-ShanxiPresentNativeFlora of China Editorial Committee, 2016
-SichuanPresentNativeFlora of China Editorial Committee, 2016
-XinjiangPresentNativeFlora of China Editorial Committee, 2016
-YunnanPresentNativeCook and Lüönd, 1982; Flora of China Editorial Committee, 2016
-ZhejiangPresentNativeFlora of China Editorial Committee, 2016
IndiaRestricted distributionNativePieterse, 1981; Cook and Lüönd, 1982; Buckingham and Bennett, 1998; EPPO, 2014; Govaerts, 2016
-Andhra PradeshPresentNativeCook, 1996; Govaerts, 2016
-Arunachal PradeshPresentNativeCook, 1996; Govaerts, 2016
-AssamPresentNativeCook, 1996; Govaerts, 2016
-BiharWidespreadCook and Lüönd, 1982; Buckingham and Bennett, 1998
-DelhiPresentNativeCook, 1996; Govaerts, 2016
-GoaPresentNativeCook, 1996; Govaerts, 2016
-GujaratPresentHaider et al., 1995; Buckingham and Bennett, 1998
-HaryanaPresentCook, 1996
-Himachal PradeshPresentCook, 1996
-Indian PunjabPresentCook, 1996
-Jammu and KashmirPresentNativeCook, 1996; Govaerts, 2016
-KarnatakaPresentCook, 1996
-KeralaPresentNativeCook, 1996; Govaerts, 2016
-Madhya PradeshPresentCook, 1996; Govaerts, 2016
-MaharashtraWidespreadCook and Lüönd, 1982; Buckingham and Bennett, 1998
-ManipurPresentNativeCook, 1996; Govaerts, 2016
-MeghalayaPresentNativeCook, 1996; Govaerts, 2016
-MizoramPresentNativeGovaerts, 2016
-OdishaPresentCook, 1996
-RajasthanPresentBuckingham and Bennett, 1998; Usha-Pandey et al., 2002
-SikkimPresentNativeGovaerts, 2016
-Tamil NaduPresentNativeCook, 1996; Govaerts, 2016
-TripuraPresentNativeGovaerts, 2016
-Uttar PradeshWidespreadCook and Lüönd, 1982; Buckingham and Bennett, 1998
-West BengalWidespreadCook and Lüönd, 1982; Buckingham and Bennett, 1998
IndonesiaRestricted distributionPieterse, 1981; Cook and Lüönd, 1982; EPPO, 2014
-JavaPresentNativeGovaerts, 2016
-MoluccasPresentNativeCook and Lüönd, 1982; Govaerts, 2016
-Nusa TenggaraPresentNativeGovaerts, 2016
-SulawesiPresentNativeGovaerts, 2016
-SumatraPresentNativeGovaerts, 2016
IranRestricted distributionCook and Lüönd, 1982; EPPO, 2014; Govaerts, 2016
IraqPresentIntroducedAl-Mandeel, 2013; Govaerts, 2016
JapanPresentNativeEPPO, 2014; Govaerts, 2016
-HonshuWidespreadCook and Lüönd, 1982
KazakhstanPresentNativeGovaerts, 2016
Korea, DPRPresentNativeEPPO, 2014; Govaerts, 2016
Korea, Republic ofRestricted distributionPieterse, 1981; Lee et al., 2001; EPPO, 2014
LaosWidespreadPieterse, 1981
LebanonRestricted distributionHolm et al., 1979; EPPO, 2014
MalaysiaWidespreadPieterse, 1981; Verkleij et al., 1983; Govaerts, 2016
-Peninsular MalaysiaPresentNativeGovaerts, 2016
MyanmarPresentNativeWaterhouse, 1993; Govaerts, 2016
NepalRestricted distributionPieterse, 1981; Verkleij et al., 1983; Cook, 1996; Rai and Pradhan, 2000; EPPO, 2014; Govaerts, 2016
PakistanRestricted distributionPieterse, 1981; Cook, 1996; Buckingham and Bennett, 1998; EPPO, 2014; Govaerts, 2016
PhilippinesRestricted distributionPieterse, 1981; EPPO, 2014; Govaerts, 2016
SingaporeWidespreadCook and Lüönd, 1982
Sri LankaRestricted distributionNativePieterse, 1981; Cook, 1996; Solangaarachchi and Perera, 2000; Wijeyaratne and Perera, 2000; EPPO, 2014; Govaerts, 2016
TaiwanPresentNativeZhuang and Beentje, 2017
ThailandRestricted distributionPieterse, 1981; Siriworakul et al., 1997; EPPO, 2014; Govaerts, 2016
VietnamRestricted distributionPieterse, 1981; EPPO, 2014; Govaerts, 2016

Africa

BurundiPresentNativePieterse, 1981; Govaerts, 2016
Congo Democratic RepublicPresentNativePieterse, 1981; Govaerts, 2016
Côte d'IvoirePresentIntroducedPieterse, 1981; Govaerts, 2016; USDA-ARS, 2016
GhanaPresentIntroducedGovaerts, 2016; USDA-ARS, 2016
KenyaRestricted distributionHolm et al., 1979; EPPO, 2014; Govaerts, 2016
MadagascarPresentNativeUSDA-ARS, 2016
MauritiusRestricted distributionCook and Lüönd, 1982; EPPO, 2014; USDA-ARS, 2016
MozambiquePresentIntroducedPieterse, 1981; Govaerts, 2016; USDA-ARS, 2016
RéunionPresentNativeCook and Lüönd, 1982; USDA-ARS, 2016
RwandaPresentNativeGovaerts, 2016
South AfricaRestricted distributionIntroduced2006 Invasive Madeira et al., 2007
Spain
-Canary IslandsRestricted distribution Not invasive Cook and Lüönd, 1982; USDA-ARS, 2011; Govaerts, 2016
TanzaniaRestricted distributionHolm et al., 1979; EPPO, 2014; Govaerts, 2016
UgandaRestricted distributionPieterse, 1981; EPPO, 2014; Govaerts, 2016
ZambiaPresentNativePieterse, 1981; Govaerts, 2016

North America

MexicoRestricted distributionIntroducedNovelo and Martinez, 1989; Rendon-Pimentil et al., 1996; Camarena and Aquilar, 1999
USAWidespreadIntroduced Invasive Pieterse, 1981; Cook and Lüönd, 1982; EPPO, 2014
-AlabamaWidespreadIntroduced Invasive Pieterse, 1981; USDA-NRCS, 2011
-ArizonaPresentIntroduced Invasive USDA-NRCS, 2011
-ArkansasWidespreadIntroducedPieterse, 1981
-CaliforniaWidespreadIntroduced Invasive Pieterse, 1981; Spencer and Ksander, 1999; USDA-NRCS, 2011
-ColoradoPresentIntroduced Invasive USDA-NRCS, 2016
-ConnecticutRestricted distributionIntroduced Invasive Les et al., 1997; USDA-NRCS, 2011
-DelawarePresentIntroducedUSDA-NRCS, 2011
-District of ColumbiaPresentIntroducedUSDA-NRCS, 2011
-FloridaWidespreadIntroduced Invasive Pieterse, 1981; Sutton and Portier, 1995; Fox et al., 1996; Sutton, 1996; Mataraza et al., 1999; Smither-Kopperl, 1999; Hanlon et al., 2000; Wheeler and Center, 2001; Cuda et al., 2002; USDA-NRCS, 2011
-GeorgiaWidespreadIntroducedPieterse, 1981; Brown and Maceina, 2002; USDA-NRCS, 2011
-IdahoRestricted distributionIntroduced2007 Invasive Jacono et al., 2011
-IndianaRestricted distributionIntroduced Invasive Alix et al., 2009; Jacono et al., 2011
-IowaPresentIntroducedUSDA-NRCS, 2011
-KansasRestricted distributionIntroduced2008Jacono et al., 2011
-KentuckyRestricted distributionIntroducedJacono et al., 2011
-LouisianaWidespreadIntroducedPieterse, 1981; Battle and Mihuc, 2000; USDA-NRCS, 2011
-MainePresentIntroduced Invasive USDA-NRCS, 2011
-MarylandPresentIntroducedUSDA-NRCS, 2011
-MassachusettsRestricted distributionIntroducedJacono et al., 2011
-MississippiWidespreadIntroduced Invasive Pieterse, 1981; USDA-NRCS, 2011
-NevadaPresentIntroduced Invasive USDA-NRCS, 2016
-New JerseyRestricted distributionIntroduced2003Jacono et al., 2011; USDA-NRCS, 2016
-New MexicoPresentIntroduced Invasive USDA-NRCS, 2016
-New YorkRestricted distributionIntroduced2008Jacono et al., 2011; USDA-NRCS, 2016
-North CarolinaWidespreadIntroduced Invasive Harlan et al., 1985; Ryan et al., 1995; USDA-NRCS, 2011
-OregonPresentIntroduced Invasive USDA-NRCS, 2016
-PennsylvaniaPresentIntroducedUSDA-NRCS, 2011
-South CarolinaWidespreadIntroduced Invasive Killgore et al., 1998; Kirk et al., 2000; Kirk et al., 2001; USDA-NRCS, 2011
-TennesseePresentIntroducedUSDA-NRCS, 2011
-TexasWidespreadIntroduced Invasive Pieterse, 1981; USDA-NRCS, 2011
-VermontPresentIntroduced Invasive USDA-NRCS, 2016
-VirginiaWidespreadIntroducedSteward et al., 1984; Everitt et al., 1999; Doyle and Smart, 2001; Owens et al., 2001; USDA-NRCS, 2011
-WashingtonPresentIntroduced Invasive USDA-NRCS, 2011
-WisconsinPresent, few occurrencesIntroduced2007Jacono et al., 2011

Central America and Caribbean

ArubaPresentIntroducedGovaerts, 2016
BarbadosPresentIntroducedBroome et al., 2007
Costa RicaPresentIntroducedRojas and Agüero, 1996; Chacón and Saborío, 2012
CubaPresentIntroduced Invasive Oviedo Prieto et al., 2012
DominicaPresentIntroduced Invasive Jérémie, 1985
GrenadaPresent, few occurrencesIntroduced1991 Invasive Lemke and Roberts, 1993; Maddi, 2009
GuadeloupePresentIntroduced Invasive Maddi et al., 2008
GuatemalaRestricted distributionIntroduced Invasive Binimelis et al., 2007
HondurasPresentIntroducedGovaerts, 2016
JamaicaPresentIntroduced Invasive I3N-Jamaica, 2016
MartiniquePresent, few occurrencesIntroduced2010 Invasive Maddi and Brizard, 2010
NicaraguaPresentIntroducedGovaerts, 2016
PanamaWidespreadIntroducedPieterse, 1981; Cook and Lüönd, 1982
Puerto RicoPresentIntroduced Invasive

South America

BrazilRestricted distributionIntroduced Invasive Sousa et al., 2009
-Sao PauloPresentIntroduced Invasive I3N-Brasil, 2016
VenezuelaPresentIntroducedSchotman, 1989

Europe

AustriaPresentIntroduced Invasive Preston and Croft, 1997; DAISIE, 2016
BelarusRestricted distribution Not invasive Tutin et al., 1972; Pieterse, 1981; Govaerts, 2016
EstoniaPresentNativeGovaerts, 2016
GermanyPresent Not invasive Tutin et al., 1972; Holm et al., 1979; Preston and Croft, 1997; DAISIE, 2016
IrelandRestricted distribution Not invasive Tutin et al., 1972; Holm et al., 1979; Cook and Lüönd, 1982; EPPO, 2014; DAISIE, 2016
ItalyPresentNativeUSDA-ARS, 2016; Zhuang and Beentje, 2017
LatviaRestricted distribution Not invasive Cook and Lüönd, 1982; EPPO, 2014; Govaerts, 2016
LithuaniaRestricted distribution Not invasive Balevicius, 1998; EPPO, 2014; Govaerts, 2016
PolandRestricted distribution Not invasive Cook and Lüönd, 1982; Klosowski and Tomaszewicz, 1997; Preston and Croft, 1997; EPPO, 2014
Russian FederationPresentNativeEPPO, 2014; Govaerts, 2016
-Central RussiaPresentNativeGovaerts, 2016
-Russian Far EastRestricted distribution Not invasive Probatova and Buch, 1981; Govaerts, 2016
-Western SiberiaPresentNativeGovaerts, 2016
SpainPresent Not invasive Holm et al., 1979
-Spain (mainland)PresentIntroducedZhuang and Beentje, 2017
UKPresent, few occurrences Not invasive Holm et al., 1979; EPPO, 2014
-England and WalesPresent, few occurrencesEPPO, 2014
-ScotlandRestricted distribution Not invasive Lansdown and Darwell, 1999

Oceania

AustraliaRestricted distributionEPPO, 2014
-Australian Northern TerritoryWidespreadSainty and Jacobs, 1981; Govaerts, 2016
-New South WalesWidespreadSainty and Jacobs, 1981; Roberts et al., 2001; Govaerts, 2016
-QueenslandWidespreadSainty and Jacobs, 1981; Balcuinas and Burrows, 1996; Hearnden and Kay, 1997; Govaerts, 2016
-South AustraliaWidespreadSainty and Jacobs, 1981; Govaerts, 2016
-VictoriaWidespreadSainty and Jacobs, 1981; Govaerts, 2016
-Western AustraliaWidespreadSainty and Jacobs, 1981; Govaerts, 2016
FijiRestricted distributionCook and Lüönd, 1982; EPPO, 2014; PIER, 2016
GuamWidespreadCook and Lüönd, 1982
New CaledoniaPresentIntroduced Invasive PIER, 2016
New ZealandRestricted distributionCook and Lüönd, 1982; Winton et al., 1996; Hofstra et al., 1999; Hofstra et al., 2001; EPPO, 2014; PIER, 2016
Papua New GuineaWidespreadCook and Lüönd, 1982; Preston and Croft, 1997; Govaerts, 2016

History of Introduction and Spread

Top of page

In the United States, H. verticillata was first imported from Ceylon (Sri Lanka) in 1947 by an aquatic plant dealer in St. Louis, Missouri to be used as an aquatic ornamental. In the early 1950s, it was introduced to the Tampa Bay area of Florida and spreading to all drainage basins in the state by the early 1970s (Langeland et al., 2008).

Early reports of introductions in Europe are believed to be via the feathers or feet of waterfowl (EPPO, 2011). Tubers and turions can also survive ingestion and regurgitation by waterfowl (ISSG, 2011).

Risk of Introduction

Top of page

The risk of introduction of H. verticillata is very high. Worldwide shipments of aquatic herbs have been found contaminated with H. verticulata and this species is still sold as an aquarium plant. H. verticillata poses a potential threat to areas outside its native habitats; this has been demonstrated in the USA and the Panama Canal area. As H. verticillata was introduced to the New World as an aquarium plant, legislative measures should be taken worldwide to restrain this trade.

Habitat

Top of page

H. verticillata can be found in freshwater in tropical and temperate regions of the world, but it can tolerate salinities of up to 7%. This species can grow in springs, lakes, marshes, ditches, rivers, and tidal zones. It is also adapted to grow in relatively low light and CO2 conditions. In areas where this species behaves as an invasive, it can be found infesting freshwater lakes, ponds, rivers, and impoundment canals.

Habitat List

Top of page
CategoryHabitatPresenceStatus
Brackish
Estuaries Secondary/tolerated habitat Harmful (pest or invasive)
Freshwater
Freshwater Present, no further details Harmful (pest or invasive)
Irrigation channels Principal habitat Harmful (pest or invasive)
Lakes Principal habitat Harmful (pest or invasive)
Ponds Present, no further details Harmful (pest or invasive)
Reservoirs Present, no further details Harmful (pest or invasive)
Rivers / streams Principal habitat Harmful (pest or invasive)
Terrestrial-natural/semi-natural
Wetlands Principal habitat Harmful (pest or invasive)

Hosts/Species Affected

Top of page

H. verticillata occurs in lowland irrigated and tidal ricefields in South-East Asia where it is most troublesome during the first half of the growth period of the crop.

Host Plants and Other Plants Affected

Top of page
Plant nameFamilyContext
Oryza sativa (rice)PoaceaeMain

Growth Stages

Top of page Seedling stage, Vegetative growing stage

Biology and Ecology

Top of page

Genetics

Hydrilla is a monotypic genus; H. verticillata is both phenotypically and genetically variable, but Cook and Lüönd (1982) do not recognize any intraspecific taxa (Preston and Croft, 1997). There are marked differences in isoenzyme patterns among strains from different regions (Verkleij and Pieterse, 1991); dioecious plants showed variation in phenoptyes of diploid (2n=16) and triploid (2n=24) accessions, however monoecious plants showed no such variation and are assumed to be ramets of the same clone (Nakamura et al., 1998). In certain cases some specific isoenzyme phenotypes can be designated as diagnostic for strains from a particular region. Material from Connecticut in the northeastern USA, is triploid and dioecious (Les et al., 1997) suggesting that it originated from a single introduction, however both diploid and triploid; and monoecious and dioecious strains occur in the USA, suggesting repeated introductions. Most introductions are likely to derive from the aquarium trade (Madeira et al., 2000).

Reproductive Biology

H. verticillata may be either monoecious or dioecious. The flowers are unisexual, arising from spathes situated in the leaf axils, each flower has three sepals and three petals. All six perianth parts are clear or translucent green (the sepals usually slightly reddish). The ovary is enclosed in the base of a hypanthium, the style is as long as the hypanthium and there are three stigmas. Due to an elongation of the hypanthium, the female flower ascends to the surface of the water. The perianth segments remain closed over the stigmas during this movement and retain a bubble of air above them. The perianth segments open to form a wide funnel which floats with its rim just at the water surface, its walls holding back the water and preventing wetting of the stigmas. The male flower becomes detached from the plant and subsequently rises to the surface of the water where the perianth segments uncurl. The anthers dehisce explosively and spread pollen for some 20 cm around the open flower. Pollination occurs via the air.

This species also reproduce vegetatively through the formation of large clones. In California and the Gulf States of the USA, and in Europe, there is no seed formation because only female flowers are produced.

Phenology

In Asia, H. verticillata produces flowers and fruits from May to October (Flora of China Editorial Committee, 2016). Although extensive flowering may occur in regions where this species has been introduced, the lack of male plants indicates that sexual reproduction is essentially non-existent.

Longevity and Activity patterns

H. verticillata is an herbaceous perennial that experiences seasonal winter dieback. In order to survive unfavourable growth conditions, this species produces two types of special hibernating organs. These structures are respectively formed in the axil of a leaf (generally described as axillary turions, turions or green turions) and at the tip of branches which grow into the hydrosoil (generally described as subterranean turions, brown turions or tubers). In 1983, it was proposed that henceforth these structures should be called axillary turion and subterranean turion (Pieterse, 1983). Both structures, which are anatomically and morphologically similar, can be considered as dormant apices or turions, i.e. short, specialized shoots of aquatic plants in which food material is stored and which eventually become detached from the mother plant. The axillary turions are stalked, cylindrical or slightly conical in shape, 3 to 12 mm long and 2 to 3.5 mm wide. Axillary turions are frequently formed on free-floating fragments. The subterranean turions are boat-shaped, 4 to 15 mm long and 2.5 to 6 mm wide, and covered by 16 to 17 whorls of tough and fleshy scale leaves.

As many as 1000 (Pieterse, 1981) to 6000 (USDA, 2011) subterranean turions may be produced per square metre in one growing season and remain viable for over 4 years (USDA, 2011). In Florida, USA, the average number of subterranean turions varies from 36 to 207 per m² and the average number of axillary turions from 5 to 90 per m² (Sutton and Portier, 1985). In areas where H. verticillata dies during the winter, the formation of turions occurs mainly in the autumn. Axillary turions are frequently formed on free-floating fragments. The formation of subterranean turions is stimulated by short days (Steward and Van, 1987). 

Associations

Dense H. verticillata beds are common aggregation sites for chain pickerel (Esox niger), whose ambush style of predation benefits from the presence of vegetative cover. In Florida, H. verticillata often occurs in mixed beds with another non-native aquatic weed Egeria densa. The two plants are very similar in appearance (Langeland et al., 2008).

Environmental Requirements

In the tropics, H. verticillata is described as tolerant of a wide variety of water conditions, from acidic and oligotrophic to eutrophic or brackish; it thrives on many kinds of pollution and tolerates a great deal of disturbance (Cook and Lüönd, 1982), although increasing salinity appears to limit its dispersal (Rout et al., 1998; Mataraza et al., 1999; Rout and Shaw, 2001). Due to its tolerance of low light conditions (White et al., 1996), it is capable of growing in water up to 7 m deep (Yeo et al., 1984). In the tropics, it forms dense monospecific stands (Valley and Bremigan, 2002). In temperate regions, it grows in alkaline, moderately calcareous, mesotrophic or slightly eutrophic waters (Preston and Croft, 1997), richer in SO4, but generally poorer in Na, K and Cl than those of Elodea canadensis (Klosowski and Tomaszewicz, 1997). It also appears to occur more often as scattered stands within more diverse aquatic plant communities (Klosowski and Tomaszewicz, 1997; Balevicius, 1998). In the USA, H. verticillata grows optimally at 20-27°C. H. verticillata exhibits moderate salinity tolerance, persisting in a laboratory environment at 7 ppt when transitioned in one step from fresh water, and at up to 12 ppt when the transfer was gradual.

Climate

Top of page
ClimateStatusDescriptionRemark
Af - Tropical rainforest climate Preferred > 60mm precipitation per month
Am - Tropical monsoon climate Preferred Tropical monsoon climate ( < 60mm precipitation driest month but > (100 - [total annual precipitation(mm}/25]))
As - Tropical savanna climate with dry summer Preferred < 60mm precipitation driest month (in summer) and < (100 - [total annual precipitation{mm}/25])
Aw - Tropical wet and dry savanna climate Preferred < 60mm precipitation driest month (in winter) and < (100 - [total annual precipitation{mm}/25])
Cs - Warm temperate climate with dry summer Tolerated Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers
Cw - Warm temperate climate with dry winter Tolerated Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)

Air Temperature

Top of page
Parameter Lower limit Upper limit
Absolute minimum temperature (ºC) 1
Mean annual temperature (ºC) 20 27

Water Tolerances

Top of page
ParameterMinimum ValueMaximum ValueTypical ValueStatusLife StageNotes
Water temperature (ºC temperature) 20-24 Optimum

Natural enemies

Top of page
Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Bagous affinis Herbivore Florida; USA
Bagous hydrillae Herbivore
Bagous laevigatus Herbivore
Cricotopus tricinctus Herbivore not specific
Ctenopharyngodon idella Herbivore California; Florida; Indonesia; Texas
Cygnus atratus Herbivore Whole plant not specific
Fusarium crookwellense Pathogen
Fusarium culmorum Pathogen Whole plant not specific
Hirschmanniella caudacrena Parasite
Hydrellia balciunasi Herbivore Leaves/Stems
Hydrellia pakistanae Herbivore Leaves/Stems USA
Labeo rohita Herbivore Whole plant not specific
Macrophomina phaseolina Pathogen
Mycoleptodiscus terrestris Pathogen Mississippi
Oreochromis zillii Herbivore
Papulaspora aspera Pathogen
Parapoynx diminutalis Herbivore Leaves/Stems Thailand
Parapoynx seminealis Herbivore not specific
Plectosphaerella cucumerina Pathogen not specific
Pythium dissotocum Leaves not specific

Notes on Natural Enemies

Top of page

Natural enemies of H. verticillata include some insect species which have potential as biological control agents. A substantial list of insects which damage H. verticillata has been produced following extensive surveys in tropical Asia and Australia. Groups which show the greatest potential are: weevils, especially of the genus Bagous (O'Brien and Askevold, 1992; Balciunas, 1985; O'Brien, 1995), such as B. affinis (Godfrey and Anderson, 1994; Buckingham and Bennett, 1998) and B. hydrillae (Balciunas et al., 1996; Wheeler and Center, 1997; Van et al., 1998), which feed on the subterranean turions; leaf-mining and stem-boring ephydrid flies, primarily of the genus Hydrellia (O'Brien and Askevold, 1992; Balciunas, 1985), including H. pakistanae (Dray and Center, 1996; Wheeler and Center, 1996; Center et al., 1997; Van et al., 1998; Wheeler and Center, 2001; Doyle et al., 2002) , H. balcuinasi (Balciunas and Burrows, 1996; Grodowitz et al., 1997), and H. purcelli (Bownes and Deeming, 2016); and leaf-feeding aquatic pyralid moths, primarily of the genus Parapoynx (Balciunas, 1985; O'Brien and Askevold, 1992), such as P. seminealis (Buckingham and Bennet, 2001) and P. diminutalis (Buckingham and Bennet, 1996; Siriworakul et al., 1997).

The grass carp (Ctenopharyngodon idella), a phytophagous fish, feeds on many aquatic plants, in particular, submerged ones. It may be considered a natural enemy of H. verticillata, although invasive forms of the plant, which are adapted to a tropical climate, do not occur in its natural habitat in China and Siberia. At present, grass carp is the most promising biological control agent for H. verticillata (Kracko and Noble, 1993; Zhu et al., 1993; Rendón-Pimental et al., 1996; Rojas and Aguero, 1996; Sutton, 1996; Killgore et al., 1998; Camarena and Aguilar, 1999; Osborne and Riddle, 1999; Maceina et al., 1999; Hanlon et al., 2000; Kirk et al., 2000).

Other species which may be considered natural enemies of H. verticillata include: the midge Cricotopus lebetis [Cricotopus tricinctus] of unknown origin (Epler et al., 2000; Cuda et al., 2002); fungal pathogens such as Mycoleptodiscus terrestris (Shearer et al., 1996; Nelson et al., 1998; Shearer, 1998; Shearer and Nelson, 2002); Plectosporium tabacinum [Monographella cucumerina] (Smither-Kopperl et al., 1999b); and Fusarium culmorum (Smither-Kopperl et al., 1998; Smither-Kopperl et al., 1999a). In New Zealand, black swans (Cygnus atratus) have been recorded grazing on H. verticillata (Hofstra et al., 1999).

For further information on natural enemies of H. verticillata in Asia, see Gopal (1990).

Means of Movement and Dispersal

Top of page

H. verticillata spreads sexually by seeds and vegetatively by plant fragments, tubers and stolons. Most commonly, pieces break free and float to new locations. It also spreads horizontally by means of branches which grow over the bottom of a water body. Vertical branches and roots are produced at nodes on these runners. Vegetative multiplication is also possible by means of fragmentation, i.e. pieces of branches, which have become detached, are able to form new, rooted plants, if they come into contact with a favourable substratum.

Accidental Introduction

In North America and elsewhere, H. verticillata has been introduced to rivers, ponds and canals as discarded fragments from aquariums or contaminants of aquatic garden plants. It is then mainly spread by recreational boats, on their motors and trailers etc. Stem pieces root in the substrate and develop into new colonies, commonly near boat ramps. Boat traffic shatters and spreads hydrilla throughout the water body (Jacono et al., 2011). 

Pathway Causes

Top of page
CauseNotesLong DistanceLocalReferences
Digestion and excretion Yes
Pet trade Yes Yes

Pathway Vectors

Top of page
VectorNotesLong DistanceLocalReferences
Floating vegetation and debris Yes
Host and vector organisms Yes
Plants or parts of plants Yes Yes
Ship hull fouling Yes
Water Yes

Impact Summary

Top of page
CategoryImpact
Animal/plant collections None
Animal/plant products None
Biodiversity (generally) Negative
Crop production None
Environment (generally) None
Fisheries / aquaculture Negative
Forestry production None
Human health None
Livestock production None
Native fauna Negative
Native flora Negative
Rare/protected species Negative
Tourism Negative
Trade/international relations None
Transport/travel Negative

Economic Impact

Top of page

Due to its rapid growth and a highly effective survival strategy, H. verticillata is one of the most troublesome aquatic weeds in the world. It rapidly outcompetes other plant species and forms dense masses, which may completely fill the volume of waterbodies. Consequently, the often multifunctional use of canals, rivers and lakes becomes seriously hampered by infestations of the weed.

Harmful effects of H. verticillata include: impeding the movement of irrigation and drainage water; hindering navigation and recreational use of the water; physical interference with hydro-electric schemes and fisheries; competition with native plants; impacts on native fauna; reductions in size and weight of sport fish (Colle and Shireman, 1980 in Jacono et al., 2011); and the creation of favourable habitats for organisms which cause or transmit disease.

Although it is increasingly troublesome in its original habitat in South-East Asia and Australia, particularly in man-made lakes and irrigation canals, its impact is most significant where it is introduced. This applies, in particular, to the USA, where it was introduced in Florida in the early 1950s (Schardt, 1995). The costs of controlling H. verticillata in Florida were reported to be $200 per ha per year (Haller, 1995) when an area of more than 12,000 ha were heavily infested in the state. Useful summaries of economic and ecological costs due to H. verticillata are provided by the Northeast Aquatic Nuisance Species Panel  (for the USA) and by Hofstra and Champion (2006) for New Zealand. On one Florida lake (Orange Lake, north-central FL), in years when H. verticillata completely covered the lake, recreational activies worth 11 million dollars were lost. In 1994-95, the state of Florida spent ~ 14.5 million dollars on H. verticillata control (Langeland,1996). 

Environmental Impact

Top of page

Impact on Habitats

H. verticillata forms dense masses, which may completely fill the volume of waterbodies. Invasion often begins in deep dark waters where most plants cannot grow. Hydrilla grows aggressively and competitively, spreading through shallower areas and forming thick mats in surface waters that may become so deep that sunlight is blocked out (Jacono et al., 2011).

Infestation has been shown to alter the physical and chemical characteristics of lakes: affecting stratification of the water column (Schmitz et al., 1993; Rizzo et al., 1996), decreasing oxygen levels (Pesacreta, 1988; Miranda and Hodges, 2000), and impeding the movement of irrigation and drainage water (Jacono et al., 2011). Dense stands also alter water quality by increasing pH and water temperature.

Impact on Biodiversity

H. verticillata outcompetes native aquatic plants. In southeast USA, it displaces native vegetation such as wild celery (Vallisneria americana) and coontail (Ceratophyllum demersum) (van Dijk, 1985; Rizzo et al., 1996 in Jacono et al., 2011).

It affects zooplankton and phytoplankton densities (Schmitz and Osbourne, 1984; Schmitz et al., 1993 in Jacono et al., 2011) and supports reduced invertebrate species diversity (Thorp et al., 1997). It has been implicated in reduced fish numbers, size and in fish kills (Rizzo et al., 1996 in Jacono et al., 2011). In a heavy infestation, predatory fish cannot hunt effectively; however ISSG (2011) notes a benefit to prey fish at <30% hydrilla cover.

Epiphytic cyanobacteria found on hydrilla are thought to be the agents producing a toxin that causes avian vacuolar myelinopathy (AVM) a disease that has killed at least 100 bald eagles (Haliaeetus leucocephalus) and thousands of American coots (Fulica americana) since 1994 in locations from Texas to North Carolina, USA (Wilde et al., 2005). The incidence of AVM is likely to increase as H. verticillata spreads. Fouts et al. (2017) report 90 bald eagle and hundreds of waterfowl deaths attributed to AVM on a reservoir on the border of Georgia and South Carolina infested with hydrilla.

Threatened Species

Top of page
Threatened SpeciesConservation StatusWhere ThreatenedMechanismReferencesNotes
Rostrhamus sociabilis plumbeus (Everglade snail kite)USA ESA listing as endangered species USA ESA listing as endangered speciesFloridaEcosystem change / habitat alterationUS Fish and Wildlife Service, 2008
Zizania texana (Texas wild-rice)USA ESA listing as endangered species USA ESA listing as endangered speciesTexasCompetition (unspecified); Ecosystem change / habitat alterationUS Fish and Wildlife Service, 1995

Social Impact

Top of page

As H. verticillata rapidly forms such dense mats, it becomes impossible to use outboard motors and to pursue fishing, swimming and other recreational activities. It can also result in reduced water flow and stagnant pools which become habitats for mosquito larvae. A case study on the social impact of Hydrilla invasions in a lake in Guatemala has been produced by Binimelis et al. (2007).

Risk and Impact Factors

Top of page Invasiveness
  • Invasive in its native range
  • Proved invasive outside its native range
  • Highly adaptable to different environments
  • Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
  • Tolerant of shade
  • Highly mobile locally
  • Long lived
  • Fast growing
  • Has high reproductive potential
  • Has propagules that can remain viable for more than one year
  • Reproduces asexually
Impact outcomes
  • Damaged ecosystem services
  • Ecosystem change/ habitat alteration
  • Infrastructure damage
  • Modification of hydrology
  • Monoculture formation
  • Negatively impacts human health
  • Negatively impacts animal health
  • Negatively impacts aquaculture/fisheries
  • Negatively impacts tourism
  • Reduced amenity values
  • Reduced native biodiversity
  • Threat to/ loss of endangered species
  • Threat to/ loss of native species
  • Transportation disruption
Impact mechanisms
  • Competition - monopolizing resources
  • Competition - shading
  • Competition - smothering
  • Competition
  • Pest and disease transmission
  • Fouling
  • Rapid growth
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Highly likely to be transported internationally deliberately
  • Difficult to identify/detect as a commodity contaminant
  • Difficult to identify/detect in the field
  • Difficult/costly to control

Uses

Top of page

H. verticillata has been used as an aquarium plant, and was first introduced to Florida when imported for this use. A dried powder from the plant has been used as detergent in the treatment of abscesses, burns and wounds (Zhuang and Beentje, 2017).

Uses List

Top of page

Environmental

  • Amenity

General

  • Pet/aquarium trade

Medicinal, pharmaceutical

  • Traditional/folklore

Diagnosis

Top of page

Although Hydrilla is generally regarded today as a monotypic genus, the species H. verticillata is very polymorphic, especially with regard to the size of the leaves and the thickness of the stems. It is, however, very difficult to distinguish the various strains as the morphology of these plants varies to a large extent with environmental factors. Chromosome numbers are not very diagnostic as in general only two cytodemes can be observed, 2n=16 and 2n=24. However, there are marked differences in isoenzyme patterns among strains from different regions (Verkleij and Pieterse, 1991). In certain cases some specific isoenzyme phenotypes can be designated as diagnostic for strains from a particular region.

Similarities to Other Species/Conditions

Top of page

Leaf characteristics are commonly used to distinguish H. verticillata from similar submerged plants in the Hydrocharitaceae, like Egeria and Elodea spp.

The sessile leaves of H. verticillata are formed in whorls at the nodes; there are 3-8, sometimes up to 12 leaves in a whorl. The leaves are 7-40 mm long, linear to lanceolate, with a conspicuous midrib. They have sharply toothed margins and spines on the vein on the lower side of the leaves; a few teeth may also be formed on this vein.

Prevention and Control

Top of page

Hydrilla can be controlled by physical, chemical and biological methods, or by a combination of these methods (integrated pest management).

Physical Control

The removal of plants either manually, using hand tools, or mechanically, using machines, is relatively expensive. Several machines, developed for aquatic weed control, can be used to remove H. verticillata plants from irrigation canals and drains; these include mowing buckets attached to a tractor or hydraulic excavator.

Different harvesters can be used to remove H. verticillata from lakes; these harvesters collect the plant material and dump it on the shore. One problem in the use of these harvesters is that cuttings of hydrilla, which are not removed from the water, help to spread the weed. Using mechanical control of hydrilla on large lakes without the use of herbicides or other control methods has not been feasible because of high cost, short-term effects and logistical constraints (Hetrick and Langeland, 2013).

In the USA, lake drawdowns are occasionally used to expose the plant and dry it out (USDA, 2011).

Chemical Control

The application of herbicides in or near waterbodies may have serious consequences for the environment and can endanger the health of local people if the water is used for drinking, swimming or washing. As a consequence, there are strict regulations for the use of chemicals to control aquatic weeds in many countries. The risk is greatest when the herbicide is introduced directly into the water, which is necessary for the control of submerged weeds.

There are many chemicals which are effective against H. verticillata but only a few of these compounds are reasonably safe for the environment and human health. One additional problem is that the use of herbicides can lead to the build up of masses of decaying plant material and, as a consequence, a sudden decrease in the oxygen content of the water.

Until recently, the main herbicide options for H. verticillata were endothal, diquat and copper. The costs of applying these contact herbicides twice a year in Florida amounted to approximately $400 per ha (Haller, 1995).

A systemic herbicide, fluridone, has been developed which can provide effective control of hydrilla; this control usually lasts for about one year. The costs in the 1990s amounted to approximately $200 per ha per year (Haller, 1995). Hydrilla biotypes with varying levels of fluridone resistance, however, have been documented in Florida (Puri et al., 2007). Benoit and Les (2013) reported an alarming increase in fluridone resistance in Florida, and the first case of resistance outside this state, from Lake Seminole in Georgia. Schmid et al. (2010) stated that the herbicide resistance in Florida had resulted in the inability to economically control large infestations of this weed. Even eight years after the last applications of fluridone in the Kissimmee Chain of Lakes in Florida, most hydrilla remained resistant (Netherland and Jones, 2015). This herbicide resistance has led to renewed interest in biological control methods (Cuda et al., 2008).

The herbicide, bensulfuron-methyl, has been tested against H. verticillata (Van and Vandiver, 1994). After one month, effective concentrations caused severe damage but regrowth occurred rapidly where herbicide exposure was limited to periods of less than 14 days. Langeland (1996) reported that while this herbicide showed promise, an Experimental Use Permit was not renewed in 1992 and efforts to register the compound were discontinued.

Since 2007, four new herbicides have been registered for hydrilla control in Florida. They include the active ingredients bispyribac-sodium, flumioxazin, penoxsulam, and imazamox (Hetrick and Langeland, 2013).

Biological Control

Biological control is theoretically the best method of controlling aquatic weed problems because the effect is lasting and relatively inexpensive. The most promising biological control agent for H. verticillata is the phytophagous fish, grass carp or white amur (Ctenopharyngodon idella). It feeds on many aquatic plants, in particular, submerged species. It is presumed that the grass carp will not breed outside its native habitat in China and Siberia as it requires special conditions for spawning. However, artificial reproduction is possible in fishery stations. In the USA, 180-320 kg/ha of grass carp is required for effective control of H. verticillata, whereas 80-70 kg/ha is sufficient in India (Pieterse, 1981).

A sterile, triploid grass carp has been bred because there is some controversy in the USA over the possibility of grass carp reproducing naturally in sufficient quantities to interfere with fisheries and waterfowl populations. This hybrid grass carp is the result of a cross between a female grass carp and a male bighead carp (Hypophthalmichthys nobilis). Control of H. verticillata using grass carp and hybrid grass carp is highly economical. In the USA, this control amounts to approximately $12 per ha per year (Haller, 1995). However, the fish needs to be retained within a certain area using fencing to prevent movement from the target site. This also allows the fish to be removed if the population needs to be managed. Fouts et al. (2017) found stakeholder support for methods of hydrilla control, including the use of sterile grass carp (Ctenopharyngodon idella) in public reservoirs in the southern USA where a neurotoxid cyanobacterial species growing on hydrilla was linked to a fatal wildlife disease.

Four insects of the genera Bagous and Hydrellia have been introduced into the USA by entomologists. These insects have eliminated large infestations of H. verticillata. Bagous affinis from India was released in Florida, USA, in 1987 (O'Brien and Pajni, 1989). This species was recently shown to have potential as a biological control agent of H. verticillata in California as it survived the winter season (Godfrey et al., 1994). Research on these insects and other potential candidates for biological control continued, and early introductions were reviewed by Center (1992).

The development of herbicide resistance in fluridone populations in Florida led to renewed interest in biological control methods (Cuda et al., 2008; Schmid et al., 2010). The study by Schmid et al. (2010) found that the leaf-mining fly Hydrellia pakistanae survived at similar levels on fluridone resistant and susceptible genotypes of hydrilla, whereas a stem-mining midge Cricotopus lebetis had lower emergence when reared on herbicide resistant genotypes. Center et al. (2013) report that Bagous hydrillae released in the southern USA had persisted and dispersed widely in the southeastern USA, but found no evidence that it has had a suppressive effect on hydrilla.

Bownes (2014; 2015) reports on the possible use of Hydrellia spp. for biological control of H. verticillata in South Africa. H. pakistanae was rejected as a biocontrol agent in favour of a Hydrellia species collected in Singapore. Bownes and Deeming (2016) suggest that Hydrellia purcelli from Singapore is a candidate biocontrol agent for this weed in South Africa.

Integrated Pest Management

An integrated approach to the control of H. verticillata had been followed in Fish Lake in Florida, USA, an area with 22 lakes in the headwaters of the Kissimmee River. This approach involved applying the herbicide, fluridone, and subsequently releasing hybrid grass carp. By 2000, however, sustained use of fluridone resulted in dominance of hydrilla strains resistant to this herbicide throughout these lakes. Last large-scale applications of fluridone were conducted in 2004, but in 2012 most of the hydrilla remained resistant (Netherland and Jones, 2015).

References

Top of page

Abreu Rodríguez E, Bernier Castrello LS, 2001. Presence of Hydrilla verticillata in Puerto Rico. (Presencia de Hydrilla verticillata, la maleza acuática perfecta en Puerto Rico.) Resúmenes Sociedad Puertorriqueña de Ciencias Agrícolas. Reunión Científica Anual. 3. http://hdl.handle.net/123456789/59

Alix MS, Scribailo RW, Price JD, 2009. Hydrilla verticillata (Hydrocharitaceae): an undesirable addition to Indiana's aquatic flora. Rhodora, 111(945):131-136. http://www.rhodora.org

Al-Mandeel FA, 2013. A new record of the invasive species Hydrilla verticillata (Linn. F.) royal on the Iraqi rivers. Advances in Environmental Biology, 7(2):384-390. http://www.aensiweb.com/aeb/2013/384-390.pdf

Aston HI, 1977. Aquatic plants of Australia. Melbourne, Australia: Melbourne University Press.

Balciunas JK, 1985. The potential for biological control of the submersed aquatic weed, Hydrilla verticillata. Proceedings of the VI International Symposium on Biological Control of Weeds Ottawa, Canada; Agriculture Canada, 487

Balciunas JK, Burrows DW, 1996. Distribution, abundance and field host-range of Hydrellia balciunasi Bock (Diptera: Ephydridae) a biological control agent for the aquatic weed Hydrilla verticillata (L.f.) Royle. Australian Journal of Entomology, 35:125-130.

Balciunas JK, Burrows DW, Purcell MF, 1996. Comparison of the physiological and realized host-ranges of a biological control agent from Australia for the control of the aquatic weed, Hydrilla verticillata. Biological Control, 7(2):148-158.

Balevicius A, 1998. The vegetation of lakes in Veisiejai Regional Park. Botanica Lithuanica, 4(3):267-284.

Battle JM, Mihuc TB, 2000. Decomposition dynamics of aquatic macrophytes in the lower Atchafalaya, a large floodplain river. Hydrobiologia, 418(1/3):123-136.

Benoit, L. K., Les, D. H., 2013. Rapid identification and molecular characterization of phytoene desaturase mutations in fluridone-resistant hydrilla (Hydrilla verticillata)., 61(1), 32-40. http://wssajournals.org/doi/abs/10.1614/WS-D-12-00018.1 doi: 10.1614/WS-D-12-00018.1

Binimelis R, Monterroso I, Rodriguez-Labajos B, 2007. A Social Analysis of the Bioinvasions of Dreissena polymorpha in Spain and Hydrilla verticillata in Guatemala. Environ Manage, 40:555-566.

Bownes, A., 2014. Suitability of a leaf-mining fly, Hydrellia sp., for biological control of the invasive aquatic weed, Hydrilla verticillata in South Africa., 59(6), 771-780. http://rd.springer.com/journal/10526 doi: 10.1007/s10526-014-9615-6

Bownes, A., 2015. A comparison of host range and performance of congeneric leaf-mining flies, Hydrellia pakistanae (Diptera: Ephydridae) and Hydrellia sp., two candidate biological control agents for the South African biotype of Hydrilla verticillata (Hydrocharitaceae)., 8444-52. http://www.sciencedirect.com/science/article/pii/S1049964415000183 doi: 10.1016/j.biocontrol.2015.02.004

Bownes, A., Deeming, J., 2016. A new species of Hydrellia (Diptera: Ephydridae) mining Hydrilla verticillata (Hydrocharitaceae) leaves in Singapore., 55(4), 353-359. http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)2052-1758

Broome R, Sabir K, Carrington S, 2007. Plants of the Eastern Caribbean. Online database. Barbados: University of the West Indies. http://ecflora.cavehill.uwi.edu/index.html

Brown SJ, Maceina MJ, 2002. The influence of disparate levels of submersed aquatic vegetation on largemouth bass population characteristics in a Georgia reservoir. Journal of Aquatic Plant Management, 40:28-35.

Buckingham GR, Bennett CA, 1996. Laboratory biology of an immigrant Asian moth, Parapoynx diminutalis (Lepidoptera: Pyralidae), on Hydrilla verticillata (Hydrocharitaceae). Florida Entomologist, 79(3):353-363.

Buckingham GR, Bennett CA, 1998. Host range studies with Bagous affinis (Coleoptera: Curculionidae), an Indian weevil that feeds on hydrilla tubers. Environmental Entomology, 27(2):469-479.

Buckingham GR, Bennett CA, 2001. Life history and laboratory host range tests of Parapoynx seminealis (Walker) (Crambidae: Nymphulinae) in Florida, U.S.A. Journal of the Lepidopterists' Society, 55(3):111-118.

Buckingham GR, Okrah EA, Christian-Meier M, 1991. Laboratory biology and host range of Hydrellia balciunasi (Diptera: Ephydridae). Entomophaga, 36(4):575-586.

Camarena M-O, Aguilar Z J-A, 1999. Biological control of aquatic weeds in Mexican Irrigation Districts. Irrigation under conditions of water scarcity. Vol 1A. 17th ICID International Congress on Irrigation and Drainage, Granada, Spain, 13-17 September 1999. New Delhi, India: International Commission on Irrigation and Drainage, 141-152.

Carvalho KM, Martin DF, 2001. Removal of aqueous selenium by four aquatic plants. Journal of Aquatic Plant Management [40th Annual Meeting of the Aquatic Plant Management Society, San Diego, California, USA, July 16-20, 2000.], 39:33-36.

Center TD, 1992. Biological control of weeds in waterways and on public lands in the southern-eastern United States of America. Proceedings of the 1st International Weed Control Congress., Vol. 1:256-263.

Center TD, Cofrancesco AF, Balciunas JK, 1990. Biological control of aquatic and wetland weeds in the southeastern United States. Proceedings of the VII International Symposium on Biological Control of Weeds., 239-262.

Center TD, Grodowitz MJ, Cofrancesco AF, Jubinsky G, Snoddy E, Freedman JE, 1997. Establishment of Hydrellia pakistanae (Diptera: Ephydridae) for the biological control of the submersed aquatic plant Hydrilla verticillata (Hydrocharitaceae) in the southeastern United States. Biological Control, 8(1):65-73.

Center, T. D., Parys, K., Grodowitz, M., Wheeler, G. S., Dray, F. A., O'Brien, C. W., Johnson, S., Cofrancesco, A., 2013. Evidence of establishment of Bagous hydrillae (Coleoptera: Curculionidae), a biological control agent of Hydrilla verticillata (Hydrocharitales: Hydrocharitaceae) in North America?, 96(1), 180-186. http://www.fcla.edu/FlaEnt/ doi: 10.1653/024.096.0124

Chacón E, Saborío G, 2012. Red Interamericana de Información de Especies Invasoras, Costa Rica. San José, Costa Rica: Asociación para la Conservación y el Estudio de la Biodiversidad. http://invasoras.acebio.org

Cook CDK, 1996. Aquatic and wetland plants of India. Oxford, UK: Oxford University Press.

Cook CDK, Gut BJ, Rix EM, Schneller J, Seitz M, 1974. Water Plants of the World: A Manual for the Identification of the Genera of Freshwater Macrophytes. The Hague, The Netherlands: Dr W Junk.

Cook CDK, Lüönd R, 1982. A revision of the genus Hydrilla (Hydrocharitaceae). Aquatic Botany, 13(4):485-504

Copeland, R. S., Nkubaye, E., Nzigidahera, B., Cuda, J. P., Overholt, W. A., 2011. The African burrowing mayfly, Povilla adusta (Ephemeroptera: Polymitarcyidae), damages Hydrilla verticillata (Alismatales: Hydrocharitaceae) in Lake Tanganyika., 94(3), 669-676. http://www.fcla.edu/FlaEnt/ doi: 10.1653/024.094.0332

Cuda JP, Coon BR, Dao YM, Center TD, 2002. Biology and laboratory rearing of Cricotopus lebetis (Diptera: Chironomidae), a natural enemy of the aquatic weed hydrilla (Hydrocharitaceae). Annals of the Entomological Society of America, 95(5):587-596.

Cuda, J. P., Charudattan, R., Grodowitz, M. J., Newman, R. M., Shearer, J. F., Tamayo, M. L., Villegas, B., 2008. Recent advances in biological control of submersed aquatic weeds., 4615-32.

DAISIE, 2016. Delivering Alien Invasive Species Inventories for Europe. European Invasive Alien Species Gateway.. www.europe-aliens.org/default.do

Doyle RD, Grodowitz M, Smart RM, Owens C, 2002. Impact of herbivory by Hydrellia pakistanae (Diptera: Ephydridae) on growth and photosynthetic potential of Hydrilla verticillata. Biological Control, 24(3):221-229.

Doyle RD, Smart RM, 2001. Effects of drawdowns and dessication on tubers of hydrilla, an exotic aquatic weed. Weed Science, 49(1):135-140.

Dray FA Jr, Center TD, 1996. Reproduction and development of the biocontrol agent Hydrellia pakistanae (Diptera: Ephydridae) on monoecious hydrilla. Biological Control, 7(3):275-280.

Epler JH, Cuda JP, Center TD, 2000. Redescription of Cricotopus lebetis (Diptera: Chironomidae), a potential biocontrol agent of the aquatic weed hydrilla (Hydrocharitaceae). Florida Entomologist, 83(2):171-180.

EPPO, 2011. Hydrilla verticillata. Mini datasheet. EPPO Alert List. http://www.eppo.org/QUARANTINE/Alert_List/invasive_plants/Hydrilla_verticillata

EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm

Everitt JH, Yang C, Escobar DE, Webster CF, Lonard RI, Davis MR, 1999. Using remote sensing and spatial information technologies to detect and map two aquatic macrophytes. Journal of Aquatic Plant Management, 37a:71-80.

Feller E, Bodle M, 1995. Hydrilla control using fluridone in lakes of central Florida. Aquatics, 17:14-16.

Flora of China Editorial Committee, 2016. Flora of China. St. Louis, Missouri and Cambridge, Massachusetts, USA: Missouri Botanical Garden and Harvard University Herbaria. http://www.efloras.org/flora_page.aspx?flora_id=2

Fouts, K. L., Poudyal, N. C., Moore, R., Herrin, J., Wilde, S. B., 2017. Informed stakeholder support for managing invasive Hydrilla verticillata linked to wildlife deaths in a Southeastern reservoir., 33(3), 260-269. http://www.tandfonline.com/loi/ulrm20 doi: 10.1080/10402381.2017.1334017

Fox AM, Haller WT, Shilling DG, 1996. Hydrilla control with split treatments of fluridone in Lake Harris, Florida. Hydrobiologia, 340(1/3):235-239.

Gallardo-Williams MT, Whalen VA, Benson RF, Martin DF, 2002. Accumulation and retention of lead by cattail (Typha domingensis), hydrilla (Hydrilla verticillata), and duckweed (Lemna obscura). Journal of Environmental Science and Health. Part A, Toxic/Hazardous Substances & Environmental Engineering, 37(8):1399-1408.

Godfrey KE, Anderson LWJ, 1994. Feeding by Bagous affinis (Coleoptera: Curculionidae) inhibits germination of hydrilla tubers. Florida Entomologist, 77(4):480-488.

Godfrey KE, Anderson LWJ, Perry SD, Dechoretz N, 1994. Overwintering and establishment potential of Bagous affinis (Coleoptera: Curculionidae) on Hydrilla verticillata (Hydrocharitaceae) in northern California. Florida Entomologist, 77(2):221-230

Gopal B, 1990. Aquatic weed problems and management in Asia. In: Pieterse AH, Murphy KJ, eds. Aquatic Weeds: the Ecology and Management of Nuisance Aquatic Vegetation. Oxford, UK: Oxford University Press, 318-340.

Govaerts R, 2016. World Checklist of Hydricharitaceae. Richmond, UK: Royal Botanic Gardens, Kew. http://apps.kew.org/wcsp/

Grodowitz MJ, Center TD, Cofrancesco AF, Freedman JE, 1997. Release and establishment of Hydrellia balciunasi (Diptera: Ephydridae) for the biological control of the submersed aquatic plant Hydrilla verticillata (Hydrocharitaceae) in the United States. Biological Control, 9(1):15-23.

Gupta M, Chandra P, 1994. Lead accumulation and toxicity in Vallisneria spiralis (L.) and Hydrilla verticillata (l.f.) Royle. Journal of Environmental Science and Health. Part A, Environmental Science and Engineering, 29(3):503-516.

Haider SW, Ganguly G, 1995. Ecological association of Sphaerodema molestum Duf (Heteroptera: Belostomatidae) with aquatic plants. Annals of Entomology, 13(1):25-27.

Haider, J. A., Höbart, R., Kovacs, N., Milchram, M., Dullinger, S., Huber, W., Essl, F., 2016. The role of habitat, landscape structure and residence time on plant species invasions in a neotropical landscape., 32(3), 240-249. http://journals.cambridge.org/action/displayFulltext?type=6&fid=10319253&jid=TRO&volumeId=32&issueId=03&aid=10319252&fulltextType=RA&fileId=S0266467416000158 doi: 10.1017/S0266467416000158

Haller WT, 1995. Hydrilla control - past, present and future. Aquatics, 17:6-8.

Hanlon SG, Hoyer MV, Cichra CE, Canfield DEJr, 2000. Evaluation of macrophyte control in 38 Florida lakes using triploid grass carp. Journal of Aquatic Plant Management, 38:48-54.

Harlan SM, Davis GJ, Pesacreta GJ, 1985. Hydrilla in three North Carolina lakes. Journal of Aquatic Plant Management, 23:68-71

Hearnden MN, Kay BH, 1997. Importance of Hydrilla verticillata (Hydrocharitaceae) as habitat for immature mosquitoes at the Ross River Reservoir, Australia. Journal of the American Mosquito Control Association, 13(2):164-170.

Hetrick SA, Langeland KA, 2013. Hydrilla Management in Florida Lakes. University of Florida, IFAS Extension. SS-AGR-361.

Hofstra DE, Champion PD, 2006. Organism Consequence Assessment: Hydrilla verticillata. Hamilton, New Zealand: National Institute for Water & Atmospheric Research Ltd, 16 pp. http://www.biosecurity.govt.nz/files/pests/hydrilla/niwa-hydrilla-consequence.pdf

Hofstra DE, Clayton JS, 2001. Evaluation of selected herbicides for the control of exotic submerged weeds in New Zealand: I. The use of endothall, triclopyr and dichlobenil. Journal of Aquatic Plant Management, 39:20-24.

Hofstra DE, Clayton JS, Champion PD, Green JD, 1999. Distribution and density of vegetative hydrilla propagules in the sediments of two New Zealand lakes. Journal of Aquatic Plant Management, 37a:41-44.

Holm LG, Pancho JV, Herberger JP, Plucknett DL, 1979. A geographical atlas of world weeds. New York, USA: John Wiley and Sons, 391 pp.

Hopple JA, Foster GD, 1996. Hydrophobic organochlorine compounds sequestered in submersed aquatic macrophytes (Hydrilla verticillata (L.F.) Royle) from the tidal Potomac River (USA). Environmental Pollution, 94(1):39-46.

I3N-Brasil, 2016. Base de dados nacional de espécies exóticas invasora (National database of exotic invasive species). Florianópolis - SC, Brazil: I3N Brasil, Instituto Hórus de Desenvolvimento e Conservação Ambiental. http://i3n.institutohorus.org.br

I3N-Jamaica, 2016. Invasive Information Network (I3N), Jamaica invasive species database.. http://apps.licj.org.jm/jamaica-invasives/

ISSG, 2011. Global Invasive Species Database (GISD). Invasive Species Specialist Group of the IUCN Species Survival Commission. http://www.issg.org/database

Jacono CC, Richerson MM, Howard Morgan V, 2011. Hydrilla verticillata fact sheet. USGS Nonindigenous Aquatic Species Database. Gainesville, Florida, USA: USGS, unpaginated. http://nas.er.usgs.gov/queries/factsheet.aspx?speciesid=6

Jérémie J, 1985. In: Adjanohoun E et al., eds. Contribution aux études ethnobotaniques et floristiques à la Dominique (Commonwealth of Dominica). Médecine traditionnelle et pharmacopée. Paris, France: Agence de Coopération Culturelle et Technique, Paris, p. 333.

Killgore KJ, Kirk JP, Foltz JW, 1998. Response of littoral fishes in upper Lake Marion, South Carolina following hydrilla control by triploid grass carp. Journal of Aquatic Plant Management, 36:82-87.

Kirk JP, Killgore KJ, Morrow JV Jr, Lamprecht SD, Cooke DW, Madsen JD, 2001. Movements of triploid grass carp in the Cooper River, South Carolina. 40th Annual Meeting of the Aquatic Plant Management Society, San Diego, California, USA, July 16-20, 2000. Journal of Aquatic Plant Management, 39:59-62.

Kirk JP, Morrow JVJr, Killgore KJ, Kozlowski SJde, Preacher JW, 2000. Population response of triploid grass carp to declining levels of hydrilla in the Santee Cooper reservoirs, South Carolina. Journal of Aquatic Plant Management, 38:14-17.

Klosowski S, Tomaszewicz H, 1997. Sociology and ecology of Hydrilletum verticillatae Tomaszewicz 1979 and Elodeetum canadensis (Pign. 1953) Pass. 1964 in north-eastern Poland. Tuexenia, No. 17:125-136.

Kracko KM, Noble RL, 1993. Herbicide inhibition of grass carp feeding on hydrilla. Journal of Aquatic Plant Management, 31:273-275.

Langeland KA, 1996. Hydrilla tuber formation in response to single and sequential bensulfuron methyl exposures at different times. In: Hydrobiologia, 340(1/3) [ed. by Caffrey, J. M.\Barrett, P. R. F.\Murphy, K. J.\Wade, P. M.]. 247-251.

Langeland KA, Cherry HM, McCormick CM, Craddock Burks KA, 2008. Identification and Biology of Non-native Plants in Florida's Natural Areas. Gainesville, Florida, USA: University of Florida IFAS Extension

Lee DoJin, Cho JuSik, Ahn HoGeun, 2001. Distribution of riparian weed species in streams of Sunchon area, Jeonnam, Korea. Korean Journal of Weed Science, 21(3):236-243.

Lemke DE, Roberts R, 1993. First record of Hydrilla verticillata (L. f.) Royle (Hydrocharitaceae) from the Lesser Antilles. Phytologia, 75: 330-332. https://www.biodiversitylibrary.org/page/13788237#page/56/mode/1up.

Les DH, Mehrhoff LJ, Cleland MA, Gabel JD, 1997. Hydrilla verticillata (Hydrocharitaceae) in Connecticut. Journal of Aquatic Plant Management, 35:10-14.

Maceina M, Slipke J, Grizzle J, 1999. Electric fences for fish? Highlights of Agricultural Research - Alabama Agricultural Experiment Station, 46(4):21-24.

Maddi FA, 2009. A short review of some aquatic plants from Grenada. Société d’Histoire naturelle L’Herminier (Nantes, France). Technical report, 31 pp. http://www.shnlh.org/ressources/pdf/botanique/rapports/GRD_Report_BOTA_2009.pdf.

Maddi FA, Brizard JP, 2010. Hydrilla verticillata (L. f.) Royle, une nouvelle espèce envahissante en Martinique? Situation actuelle et prospective. Bulletin de la Societé des sciences naturelles de lÓuest de la France, nouvelle série, 32(1): 16-31. http://www.shnlh.org/ressources/pdf/botanique/articles/MADDI_2010_Ssnof_32.pdf.

Maddi FA, Meurgey F, Delacruz C, 2008. Hydrilla verticillata. (L.f.) Royle in Guadeloupe, French West Indies. Journal of Aquatic Plant Management, 46: 196-198. https://www.apms.org/wp/wp-content/uploads/2012/10/v46p196_2008.pdf.

Madeira PT, Coetzee JA, Center TD, White EE, Tipping PW, 2007. The origin of Hydrilla verticillata recently discovered at a South African dam. Aquatic Botany, 87(2):176-180. http://www.sciencedirect.com/science/journal/03043770

Madeira PT, Jacono CC, Van TK, 2000. Monitoring hydrilla using two RAPD procedures and the Nonindigenous Aquatic Species database. Journal of Aquatic Plant Management, 38:33-40.

Madeira PT, Van TK, Steward KK, Schnell RJ, 1997. Random amplified polymorphic DNA analysis of the phenetic relationships among world-wide accessions of Hydrilla verticillata. Aquatic Botany, 59(3/4):217-236.

Mariappan V, Rajan MR, Bhuvaneswari K, 2002. Recycling of treated tannery effluent using aquatic macrophytes. Environment and Ecology, 20(3):685-688.

Mataraza LK, Terrell JB, Munson AB, Canfield DEJr, 1999. Changes in submersed macrophytes in relation to tidal storm surges. Journal of Aquatic Plant Management, 37:3-12.

Miranda LE, Hodges KB, 2000. Role of aquatic vegetation coverage on hypoxia and sunfish abundance in bays of a eutrophic reservoir. Hydrobiologia, 427(1/3):51-57.

Missouri Botanical Garden, 2016. Tropicos database. St. Louis, Missouri, USA: Missouri Botanical Garden. http://www.tropicos.org/

Nelson LS, Shearer JF, Netherland MD, 1998. Mesocosm evaluation of integrated fluridone-fungal pathogen treatment on four submersed plants. In: Journal of Aquatic Plant Management, 36. 73-77.

Netherland MD, 1997. Turion ecology of hydrilla. Journal of Aquatic Plant Management, 35:1-10.

Netherland MD, Shearer JF, 1996. Integrated use of fluridone and a fungal pathogen for control of hydrilla. Journal of Aquatic Plant Management, 34:4-8.

Netherland, M. D., Jones, D., 2015. Fluridone-resistant hydrilla (Hydrilla verticillata) is still dominant in the Kissimmee Chain of Lakes, FL., 8(2), 212-218. http://www.bioone.org/loi/ipsm doi: 10.1614/IPSM-D-14-00071.1

Ni RuFeng, Huang NengGeng, 1997. Studies on dynamic simulation for fishery resources system in Gehu Lake. Journal of Fisheries of China, 21(4):398-403.

Novelo A, Martínez M, 1989. Hydrilla verticillata (Hydrocharitaceae), problem aquatic weed recently introduced in Mexico. Anales del Instituto de Biología. Serie Botánica, 58:97-102.

O'Brien C, Pajni HR, 1989. Two Indian Bagous weevils (Coleoptera, Curculionidae), tuber feeders of Hydrilla verticillata (Hydrocharitaceae), one a potential biocontrol agent in Florida. Florida Entomologist, 72(3):462-468.

O'Brien CW, 1995. Curculionidae, premiere biocontrol agents (Coleoptera: Curculionidae). Memoirs of the Entomological Society of Washington [In Biology and Phylogeny of Curculionoidea: Proceedings of a symposium convened at the XVIII International Congress of Entomology, Vancouver, Canada, 3-9 July, 1988.], No. 14:119-128.

O'Brien CW, Askevold IS, 1992. Systematics and evolution of weevils of the genus Bagous Germar (Coleoptera: Curculionidae) I. Species of Australia. Transactions of the American Entomological Society, 118(4):331-452.

Osborne JA, Riddle RD, 1999. Feeding and growth rates for triploid grass carp as influenced by size and water temperature. Journal of Freshwater Ecology, 14(1):41-45; 10 ref.

Oviedo Prieto R, Herrera Oliver P, Caluff MG, et al. , 2012. National list of invasive and potentially invasive plants in the Republic of Cuba - 2011. (Lista nacional de especies de plantas invasoras y potencialmente invasoras en la República de Cuba - 2011). Bissea: Boletín sobre Conservación de Plantas del Jardín Botánico Nacional de Cuba, 6(Special Issue 1):22-96.

Owens CS, Madsen JD, Smart RM, Stewart RM, 2001. Dispersal of native and nonnative aquatic plant species in the San Marcos River, Texas. Journal of Aquatic Plant Management, 39:75-79.

Pandey DK, 1996. Relative toxicity of allelochemicals to aquatic weeds. Allelopathy Journal, 3(2):241-246.

Pennington TG, Skogerboe JG, Getsinger KD, 2001. Herbicide/copper combinations for improved control of Hydrilla verticillata. Journal of Aquatic Plant Management [40th Annual Meeting of the Aquatic Plant Management Society, San Diego, California, USA, July 16-20, 2000.], 39:56-58.

Pesacreta G, 1988. Water chemistry from North Carolina piedmont impoundments with hydrilla (Hydrilla verticillata (L.) Royle). Ph.D. dissertation, North Carolina State University, Raleigh, NC, USA.

PIER, 2016. Pacific Islands Ecosystems at Risk. Honolulu, USA: HEAR, University of Hawaii. http://www.hear.org/pier/index.htm

Pieterse AH, 1981. Hydrilla verticillata - a review. Abstracts on Tropical Agriculture, 7(6):9-34.

Pieterse AH, 1983. Announcement. Aquatic Botany, 16:313.

Pieterse AH, Ebbers AEH, Verkleij JAC, 1984. A comparative study on isoenzyme patterns in Hydrilla verticillata (L.F.) Royle from Ireland and north eastern Poland. Aquatic Botany, 18(3):299-303.

Posey MH, Wigand C, Stevenson JC, 1993. Effects of an introduced aquatic plant, Hydrilla verticillata, on benthic communities in the Upper Chesapeake Bay. Estuarine, Coastal & Shelf Science, 37(5):539-555.

Preston CD, Croft JM, 1997. Aquatic plants in Britain and Ireland. Colchester, UK: Harley.

Probatova NS, Buch TG, 1981. Hydrilla verticillata (Hydrocharitaceae) in the Soviet Far East. Botanicheskii Zhurnal, 66(2):208-214

Puri, A., MacDonald, G. E., Haller, W. T., Megh Singh, 2007. Growth and reproductive physiology of fluridone-susceptible and -resistant hydrilla (Hydrilla verticillata) biotypes., 55(5), 441-445. http://wssa.allenpress.com/wssaonline/?request=get-abstract&issn=0043-1745&volume=055&issue=05&page=0441 doi: 10.1614/WS-07-020.1

Rai AK, Pradhan BR, 2000. Aquatic weeds in the Lakes Phewa, Begnas and Rupa in Pokhara Valley, Nepal. Veterinary Review (Kathmandu), 15:10-12.

Rajni Kant, Pandey SD, Sharma SK, 1996. Mosquito breeding in relation to aquatic vegetation and some physico-chemical parameters in rice fields of central Gujarat. Indian Journal of Malariology, 33(1):30-40.

Rendón-Pimentel L, Guillén-González JA, Mosqueda-Badillo R, 1996. The training programme for the Water Users' Associations in Mexico. Sustainability of irrigated agriculture - farmers' participation towards sustainable agriculture: volume 1-B. Transactions of the 16th International Congress on Irrigation and Drainage, Cairo, Egypt, 1996., 495-504.

Rizzo WM, Boustany RG, Meaux DR, 1996. Ecosystem changes in a a subtropical Louisiana lake due to invasion by Hydrilla. In: From Small Streams to Big Rivers, Society of Wetland Scientists 17th Annual Meeting, June 9-14, 1996, Kansas City, MO, USA.

Roberts DE, Sainty GR, Cummins SP, Hunter GJ, Anderson LWJ, 2001. Managing submersed aquatic plants in the Sydney International Regatta Centre, Australia. Journal of Aquatic Plant Management, 39:12-17.

Rojas M, Agüero R, 1996. Biological control of Hydrilla verticillata Vahl by utilization of the grass carp (Ctenopharyngodon idella Vía). Agronomia Mesoamericana, 7(2):1-12.

Rout NP, Shaw BP, 2001. Salt tolerance in aquatic macrophytes: possible involvement of the antioxidative enzymes. Plant Science, 160(3):415-423.

Rout NP, Tripathi SB, Shaw BP, 1998. Effect of salinity on chlorophyll and proline contents in three aquatic macrophytes. Biologia Plantarum, 40(3):453-458.

Ryan FJ, Coley CR, Kay SH, 1995. Coexistence of monoecious and dioecious hydrilla in Lake Gaston, North Carolina and Virginia. Journal of Aquatic Plant Management, 33:8-12.

Sainty GR, Jacobs SWL, 1981. Waterplants of New South Wales. New South Wales, Australia: Water Resources Commission.

Schardt J, 1995. Hydrilla reaches crisis levels in Florida waters. Aquatics, 17:10-12.

Schmid, T. A., Cuda, J. P., MacDonald, G. E., Gillmore, J. L., 2010. Performance of two established biological control agents on hydrilla genotypes susceptible and resistant to fluridone herbicide., 48102-105. http://www.apms.org/japm/vol48/vol48p102.pdf

Schmitz DC, Osbourne JA, 1984. Zooplankton densities in a Hydrilla infested lake. Hydrobiologia, 111:127-132.

Schmitz DC, Schardt JD, Leslie AJ, Dray FA Jr, Osborne JA, Nelson BV, 1993. The ecological impact and management history of three invasive alien aquatic plant species in Florida. In: Biological pollution: the control and impact of invasive exotic species. Proceedings of a symposium held at Indianapolis, Indiana, USA, 25-26 October 1991 [ed. by McKnight, B.N.]. Indianapolisna, USA, India: Indiana Academy of Science, 173-194.

Schotman CYL, 1989. Plant pests of quarantine importance to the Caribbean. RLAC-PROVEG, No. 21:80 pp.

Shearer JF, 1996. Development of a fungal pathogen for biocontrol of the submersed aquatic macrophyte Hydrilla verticillata. In: Proceedings of the 9th international symposium on biological control of weeds, Stellenbosch, South Africa, 19-26 January 1996 [ed. by Moran, V. C.\Hoffmann, J. H.]. Rondebosch, South Africa: University of Cape Town, 473-477.

Shearer JF, 1998. Biological control of hydrilla using an endemic fungal pathogen. In: Journal of Aquatic Plant Management, 36. 54-56.

Shearer JF, Nelson LS, 2002. Integrated use of endothall and a fungal pathogen for management of the submersed aquatic macrophyte Hydrilla verticillata. Weed Technology, 16(1):224-230.

Siriworakul M, Benyasut S, Wanasiri P, 1997. Study, survey, and evaluation of natural enemies of aquatic weeds in irrigation systems. Kaen Kaset = Khon Kaen Agriculture Journal, 25(2):58-61.

Smither-Kopperl ML, Charudattan R, Berger RD, 1998. Dispersal of spores of Fusarium culmorum in aquatic systems. Phytopathology, 88(5):382-388.

Smither-Kopperl ML, Charudattan R, Berger RD, 1999. Deposition and adhesion of spores of Fusarium culmorum on hydrilla. Canadian Journal of Plant Pathology, 21(3):291-297.

Smither-Kopperl ML, Charudattan R, Berger RD, 1999. Plectosporium tabacinum, a pathogen of the invasive aquatic weed Hydrilla verticillata in Florida. Plant Disease, 83(1):24-28; 24 ref.

Soerjani M, Kostermans AJGH, Tjitrosoepomo G, 1987. Weeds of Indonesia. Jakarta, Indonesia: Balai Pustaka, 716 pp.

Solangaarachchi SM, Perera WMDSK, 1996. Preliminary studies on changes in distribution of aquatic macrophytes in the Lunuwila tank in 1991-1993, after introduction of Cyrtobagous salviniae to control Salvinia molesta. Journal of the National Science Council of Sri Lanka, 24(2):81-94.

Sousa WTZ, Thomaz SM, Murphy KJ, Silveira MJ, Mormul RP, 2009. Environmental predictors of the occurrence of exotic Hydrilla verticillata (L.f.) Royle and native Egeria najas Planch. in a sub-tropical river floodplain: the Upper River Paraná, Brazil. Hydrobiologia, 632:65-78. http://springerlink.metapress.com/content/1573-5117/

Spencer DF, Ksander GG, 1995. Differential effects of the microbial metabolite, acetic acid, on sprouting of aquatic plant propagules. Aquatic Botany, 52(1-2):107-119.

Spencer DF, Ksander GG, 1997. Dilute acetic acid exposure enhances electrolyte leakage by Hydrilla verticillata and Potamogeton pectinatus tubers. Journal of Aquatic Plant Management, 35:25-30.

Spencer DF, Ksander GG, 1999. Influence of dilute acetic acid treatments on survival of monoecious hydrilla tubers in the Oregon House Canal, California. Journal of Aquatic Plant Management, 37a:67-71.

Stevens PF, 2012. Angiosperm Phylogeny Website.. http://www.mobot.org/MOBOT/research/APweb/

Steward KK, 1997. Influence of photoperiod on tuber production in various races of Hydrilla (Hydrilla verticillata). Hydrobiologia, 354:57-62.

Steward KK, 2000. Influence of photoperiod on vegetative propagule production in three turion-producing races of Hydrilla verticillata (L.f.) Royle. Hydrobiologia, 432(1/3):1-8.

Steward KK, Van TK, 1987. Comparative studies of monoecious and dioecious hydrilla (Hydrilla verticillata) biotypes. Weed Science, 35(2):204-210.

Steward KK, Van TK, Carter V, Pieterse AH, 1984. Hydrilla invades Washington, D.C. and the Potomac. American Journal of Botany, 71(1):162-163

Sutton DL, 1996. Depletion of turions and tubers of Hydrilla verticillata in the North New River Canal, Florida. Aquatic Botany, 53(1/2):121-130.

Sutton DL, Portier KM, 1985. Density of tubers and turions of hydrilla in south Florida. Journal of Aquatic Plant Management, 23:64-67

Sutton DL, Portier KM, 1995. Growth of dioecious hydrilla in sediments from six Florida lakes. Journal of Aquatic Plant Management, 33:3-7.

Swarbrick JT, Finlayson CM, Cauldwell AJ, 1981. The biology of Australian weeds. 7. Hydrilla verticillata (L.f.) Royle. Journal of the Australian Institute of Agricultural Science, 47(4):183-190.

Thorp AG, Jones RC, Kelso DP, 1997. A comparison of water-column macroinvertebrate communities in beds of differing submersed aquatic vegetation in the tidal freshwater Potomac River. Estuaries, 20(1):86-95.

Tutin TG, Heywood VH, Burges NA, Moore DM, Valentine DH, Walters SM, Webb DA, 1972. Flora Europaea. Vol. 3. Diapensiaceae to Myoporaceae. London, Cambridge University Press., UK xxix+370pp.

US Fish and Wildlife Service, 1995. In: San Marcos and Comal and Associated Aquatic Ecosystems (Revised) Recovery Plan. US Fish and Wildlife Service, x + 93 pp. + 28 pp. of appendices.

US Fish and Wildlife Service, 2008. In: Everglade Snail Kite, Rostrhamus sociabilis plumbeus, 5-Year Review: Summary and Evaluation. US Fish and Wildlife Service, 21 pp. + appendices.

USDA, 2011. Hydrilla verticillata Royle. Draft Federal Noxious Weed List Fact Sheet. Unpublished, available from USDA.

USDA-ARS, 2011. Germplasm Resources Information Network (GRIN). Online Database. Beltsville, Maryland, USA: National Germplasm Resources Laboratory. https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysearch.aspx

USDA-ARS, 2016. Germplasm Resources Information Network (GRIN). Online Database. National Germplasm Resources Laboratory, Beltsville, USA. http://www.ars-grin.gov/cgi-bin/npgs/html/tax_search.pl

USDA-NRCS, 2011. The PLANTS Database. Baton Rouge, USA: National Plant Data Center. http://plants.usda.gov/

USDA-NRCS, 2016. The PLANTS Database. Baton Rouge, USA: National Plant Data Center. http://plants.usda.gov/

Usha Pandey, Alka Jain, 2002. Mineral status of some macrophytes growing at Gap sagar lake, Dungarpur, Rajasthan. Plant Archives, 2(2):161-163.

Vajpayee P, Rai UN, Sinha S, Tripathi RD, Chandra P, 1995. Bioremediation of tannery effluent by aquatic macrophytes. Bulletin of Environmental Contamination and Toxicology, 55(4):546-553.

Valley RD, Bremigan MT, 2002. Effects of macrophyte bed architecture on largemouth bass foraging: implications of exotic macrophyte invasions. Transactions of the American Fisheries Society, 131(2):234-244.

Van Dijk G, 1985. Vallisneria and its interactions with other species. Aquatics, 7(3):6-10.

Van TK, Vandiver VVJr, 1994. Response of hydrilla to various concentrations and exposures of bensulfuron methyl. Journal of Aquatic Plant Management, 32:7-11.

Van TK, Wheeler GS, Center TD, 1998. Competitive interactions between hydrilla (Hydrilla verticillata) and vallisneria (Vallisneria americana) as influenced by insect herbivory. Biological Control, 11(3):185-192.

Verkleij JAC, Pieterse AH, 1991. Isoenzyme patterns in leaves of Hydrilla verticillata (Hydrocharitaceae). In: Triest L, ed. Opera Botanica Belgica vol. 4, Isoenzymes in water plants. Meise, Belgium: National Botanic Garden of Belgium, 49-57.

Verkleij JAC, Pieterse AH, Horneman GJT, Torenbeek M, 1983. A comparative study of the morphology and isoenzyme pattern of Hydrilla verticillata (L.f.) Royale. Aquatic Botany, 17(1):43-59.

Waterhouse DF, 1993. The Major Arthropod Pests and Weeds of Agriculture in Southeast Asia. ACIAR Monograph No. 21. Canberra, Australia: Australian Centre for International Agricultural Research, 141 pp.

Wheeler GS, Center TD, 1996. The influence of hydrilla leaf quality on larval growth and development of the biological control agent Hydrellia pakistanae (Diptera: Ephydridae). Biological Control, 7(1):1-9.

Wheeler GS, Center TD, 1997. Growth and development of the biological control agent Bagous hydrillae as influenced by hydrilla (Hydrilla verticillata) stem quality. Biological Control, 8(1):52-57.

Wheeler GS, Center TD, 2001. Impact of the biological control agent Hydrellia pakistanae (Diptera : Ephydridae) on the submersed aquatic weed Hydrilla verticillata (Hydrocharitaceae). Biological Control, 21(2):168-181.

White A, Reiskind JB, Bowes G, 1996. Dissolved inorganic carbon influences the photosynthetic responses of Hydrilla to photoinhibitory conditions. Aquatic Botany, 53(1/2):3-13.

Wijeyaratne MJS, Perera WMDSK, 2000. Studies on the feasibility of using indigenous fishes for controlling aquatic macrophytes in Sri Lanka. Journal of Aquaculture in the Tropics, 15(3):253-260.

Wilde SB, Murphy TM, Hope CP, Habrun SK, Kempton J, Birrenkott A, Wiley F, Bowerman WW, Lewitus AJ, 2005. Avian vacuolar myelinopathy linked to exotic aquatic plants and a novel cyanobacterial species. Environmental Toxicology, 20(3):348-353. http://www3.interscience.wiley.com/cgi-bin/abstract/110494261/ABSTRACT

Winton MD de, Clayton JS, de Winton MD, 1996. The impact of invasive submerged weed species on seed banks in lake sediments. Aquatic Botany, 53(1-2):31-45.

Yeo RR, Falk RH, Thurston JR, 1984. The morphology of hydrilla ((Hydrilla verticillata) (L.f.) Royle). Journal of Aquatic Plant Management, 22:1-17.

Zhang ShengZhao, Wang GuoXiang, Pu PeiMin, Chigira T, 1999. Succession of hydrophytic vegetation and swampy tendency in the East Taihu Lake. Journal of Plant Resources and Environment, 8(2):1-6.

Zhou Jin, Chen JiaKuan, 1996. Phytocoenological studies on floating-leaved anchored aquatic plants in Futouhu Lake, Hubei Province. II. The structure of Comm. Nymphoides peltata. Acta Hydrobiologica Sinica, 20(1):49-56.

Zhu QS, Zhou G, Yu N, Yu N, Lu QP, 1993. Transplanting of aquatic fodder plants in Lake Ge Hu in relation to its effectiveness for pen fish farming. Journal of Fisheries of China, 17(3):189-197; 17 ref.

Zhuang, X., Beentje, H.J., 2017. Hydrilla verticillata. The IUCN Red List of Threatened Species 2017: e.T167871A65905991. http://dx.doi.org/10.2305/IUCN.UK.2017-1.RLTS.T167871A65905991.en

Contributors

Top of page

17/08/16 Updated by:

Julissa Rojas-Sandoval, Department of Botany-Smithsonian NMNH, Washington DC, USA

Distribution Maps

Top of page
You can pan and zoom the map
Save map